const symbol = (() => {
    let cache = new Map()
    function fn() {
        if (this instanceof fn) {
            throw new Error("不可以new")
        }
    }
    // 找value
    fn.for = function (key) {
        if (!cache.has(key)) {
            cache.set(key, {})
        }
        return cache.get(key)
    }
    // 找key
    fn.keyof = function (val) {
        for (const [k, v] in object) {
            if (v == val) {
                return v

            }
        }
    }

    return fn

})()